In general, power transfer mechanisms, such as transfer cases, may be operatively associated with either manual or automatic transmissions for selectively directing power from an engine to a first set of driven wheels in a two-wheel drive mode, as well as selectively directing power to a second set of wheels for operation in a four-wheel drive mode. Many transfer cases provide for a mode shift when transferring between two-wheel and four-wheel drive modes, as well as a range shift to provide at least two different reduction ratios to the driven wheels.
Some transfer cases include a range shift system axially translating a range sleeve between low range, neutral and high range positions. The range shift system may include a range shift fork for the application of force to the range sleeve. To achieve a range shift, an actuator typically including a relatively large electric motor, applies a force to the range shift fork. Other mechanical torque transferring devices may be positioned between electric motor and the range shift fork to multiply the apply force provided to the range shift fork. For example, some range shift systems include ball ramp actuators, pilot clutches, and the like.
In some arrangements, the magnitude of force required at the range shift fork to complete a range shift may be significant. Accordingly, the size of the electric motor and the quantity of energy required to complete a shift may be greater than desired. As such, it may be desirable to provide a range shift system operable to use the energy from a driveline component to complete a range shift.